Frequently, in the installation, testing and maintenance of pipelines it becomes necessary to interrupt the flow of the material contained within the pipeline or to seal off areas of the pipeline and divert the flow. Plugs which are inflatable are widely used and have proven extremely reliable in service. It is extremely likely that workmen will have to be protected only by the effectiveness of the plug when working downstream from the fluid flow. Thus, it is essential that these plugs operate in their intended manner. Currently a wide variety of different types of plugs are on the market which generally perform satisfactorily.
The following patents reflect the state of the art of which applicant is aware and are included to discharge applicant's acknowledged duty to disclose known prior art. However, it is respectfully stipulated that none of these patents teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as set forth hereinafter and as especially claimed.
______________________________________ INVENTOR PATENT NO. ISSUE DATE ______________________________________ Bride, C. T. 539,568 May 21, 1895 Raflovich, G. H. 1,048,208 December 24, 1912 Foote, F. J. 1,240,433 September 18, 1917 Burdette, R. S. 1,549,962 August 18, 1925 Goodman, P. 1,760,750 May 27, 1930 Biggs, N. W. 1,842,652 January 26, 1932 Svirsky, B. 2,299,116 October 20, 1942 Charnes, J. E. 2,476,817 July, 19, 1949 Cunningham, M. M. 2,559,064 July 3, 1951 Cunningham, M. M. 2,612,924 October 7, 1952 Cunningham, M. M. 2,613,169 October 7, 1952 Webber, E. G. 2,623,571 December 30, 1952 Prager, W. 2,672,902 March 23, 1954 Vanderlans, C. J. F. 2,927,609 March 8, 1960 Stringham IIII, E. B. 3,103,235 September 10, 1963 Zurbrigen, J. A. et al. 3,168,909 February 9, 1965 Telford, E. B. et al. 3,269,421 August 30, 1966 Daley, D. R. et al. 3,618,639 November 9, 1971 Conklin et al. 3,750,711 August 7, 1973 Home et al. 3,763,896 October 9, 1973 Larson 3,834,422 September 10, 1974 Home et al. 3,874,926 Apru 1, 1975 Beinhaur 3,897,088 July 29, 1975 Larson 3,951,173 April 20, 1976 Home et al. 4,025,360 May 24, 1977 Vanderlans 4,070,904 January 31, 1978 Vanderlans 4,079,755 March 21, 1978 Larson 4,096,997 June 27, 1978 Vanderlans 4,182,642 January 8, 1980 Moolenaar 4,274,206 June 23, 1981 Vetter 4,377,184 March 22, 1983 Vanderlans 4,421,698 December 20, 1983 Gerber 4,446,983 May 8, 1984 Champleboux 4,467,835 August 28, 1984 Ragout 4,467,836 August 28, 1984 Mathison et al. 4,493,344 January 15, 1985 Vetter 4,612,961 September 23, 1986 Mathison et al. 4,614,206 September 30, 1986 Carruthers 4,627,470 December 9, 1986 Mathison 4,691,728 September 8, 1987 Knutar 4,721,397 January 26, 1988 Mathison et al. 4,763,511 August 16, 1988 Mathison Des. 300,350 March 21, 1989 Mathison et al. 4,817,671 April 4, 1989 Vetter 4,883,094 November 28, 1989 ______________________________________
Mechanics of Pneumatic Tires; U.S. National Bureau of Standards; Joseph D. Walter; Issued: Nov. 1971; pp 405-421 PA0 So. Ca.P; General Catalogue; Date of Issue and author unknown PA0 Uniroyal Brochure "Uniroyal Pipe Stoppers"; Uniroyal, Inc., Engineered Systems Depts.; Date of Issue unkown
The patent granted to applicant, U.S. Pat. No. 4,079,755, teaches the use of an inflatable plug provided with unidirectional fibers skewed with respect to the long axis of the plug which controls the expansion of the plug upon inflation. While this device is extremely durable in construction and safe to use, the instant application is directed to ongoing evolutionary improvements when contrasted with this known prior art. One area of improvement involves the reinforcement that is provided in the instant invention at the terminal extremities of a plug.
The patent to Goodman U.S. Pat. No. 1,760,750, teaches the use of a stopper for gas and water mains in which longitudinal strengthening tapes coact with reinforcing tapes at one end of a plug to reliably support means at one end of the plug for drawing the stopper into position in the main. The instant invention is distinguished over the Goodman patent in many ways both structurally and functionally, with the net result being improved performance in all aspects.
The remaining citations show the state of the art further and diverge more starkly from the instant invention. More particularly, these plugs are prone to failure where the plug body co-joins with end plate components which traditionally serve as hosts for valves, pull-rings and the like. Most plugs are pneumatically expanded to seal off the conduit. Reaction forces exist between end plates and the plug body and exhibit a tendency to fail at that point since rigid end plates do not expand and the body portion must. Thus, in use, there is a tendency of the plug body to try and peal away from the end plates. Reinforcing this area has been the focus of many lay-up techniques.
Because the nature of the plug seal within the conduit involves pressure between the body member of the plug and an interior wall of the conduit, failure of the plug, for example by fatigue or inadvertent over inflation can cause injury to personnel near the plug.